Sulfur tolerance of Fe promoted BaO/Al2O3 systems as NOx storage materials

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buir.advisorÖzensoy, Emrah
dc.contributor.authorParmak, Emrah
dc.date.accessioned2016-01-08T18:15:07Z
dc.date.available2016-01-08T18:15:07Z
dc.date.issued2011
dc.departmentDepartment of Chemistryen_US
dc.descriptionAnkara : The Department of Chemistry and the Graduate School of Engineering and Science of Bilkent University, 2011.en_US
dc.descriptionThesis (Master's) -- Bilkent University, 2011.en_US
dc.descriptionIncludes bibliographical references leaves 62-65.en_US
dc.description.abstractTernary mixed oxide systems in the form of BaO/FeOx/Al2O3 were studied with varying compositions as an alternative to the conventional NOx storage materials (i.e. BaO/Al2O3). NOx uptake properties of the freshly prepared samples, sulfur adsorption and NOx storage in the presence of sulfur were investigated in order to elucidate the sulfur tolerance of these advanced NOx storage systems in comparison to their conventional counterparts. The structural characterization of the poisoned NOx storage materials was analyzed by means of scanning electron microscopy (SEM). The performance and sulfur tolerance of these materials upon SOx adsorption were monitored by in-situ Fourier transform infrared (FTIR) spectroscopy, temperature programmed desorption (TPD) and X-Ray Photoelectron Spectroscopy (XPS). Addition of FeOx domains to the conventional BaO/Al2O3 system was observed to introduce additional NOx storage sites and tends to increase the total NOx uptake capacity. SO2+O2 adsorption on the investigated samples was found to lead to the formation of sulfites at low temperatures which are converted into surface and bulk sulfates with increasing temperatures. After annealing at 1173 K in vacuum most of the sulfates can be removed from the surface and the samples can be regenerated. However, for Fe/Ba/Al samples formation of various highly-stable sulfite and sulfate species were also observed which survive on the surface even after annealing at elevated temperatures (1173 K). Sulfur poisoning on 5(10)Fe/8Ba/Al samples leads to preferential poisoning of the FeOx, Al2O3 and surface BaO sites where bulk BaO sites seems to be more tolerant towards sulfur poisoning. In contrast, sulfur poisoning occurs in a rather non-preferential manner on the 5(10)Fe/20Ba/Al samples influencing all of the NOx storage sites. Thermal stability of the sulfate species seem to increase in the following order: surface alumina sulfates < surface Ba sulfates ≈ Fe sulfates < bulk Ba sulfates ≈ bulk alumina sulfates < highly stable sulfates and sulfites on Fe/Ba/Al surfaces. In overall, it can be argued that the Fe promotion has a positive influence on the NOx storage capacity as well as a positive effect on the sulfur tolerance when the Ba loading is equal to 8 wt% (i.e. 5(10)Fe/8Ba/Al). For these samples, even the surface uptakes more SOx than conventional 8Ba/Al system, NOx uptake properties as well as thermal regeneration properties seem slightly improved. On the other hand, for higher Ba loadings (i.e. 5(10)Fe/20Ba/Al) Fe promotion has a minor positive effect on NOx uptake capacity and SOx tolerance for 5 wt% Fe promotion while 10 wt% Fe promotion seems to have no positive influence.en_US
dc.description.degreeM.S.en_US
dc.description.statementofresponsibilityParmak, Emrahen_US
dc.format.extentxvii, 65 leavesen_US
dc.identifier.itemidB130064
dc.identifier.urihttp://hdl.handle.net/11693/15218
dc.language.isoEnglishen_US
dc.publisherBilkent Universityen_US
dc.rightsinfo:eu-repo/semantics/openAccessen_US
dc.subjectNSRen_US
dc.subjectNOx storage materialsen_US
dc.subjecty-Al2O3en_US
dc.subjectBa/Alen_US
dc.subjectFe/Ba/Alen_US
dc.subjectSOx poisoningen_US
dc.subjectFTIR spectroscopyen_US
dc.subjectTPDen_US
dc.subjectXPS and SEM-EDXen_US
dc.subject.lccQD181.N1 P37 2011en_US
dc.subject.lcshNitrogene oxides.en_US
dc.subject.lcshOxidation.en_US
dc.subject.lcshCatalysis.en_US
dc.subject.lcshSulfur compounds.en_US
dc.titleSulfur tolerance of Fe promoted BaO/Al2O3 systems as NOx storage materialsen_US
dc.typeThesisen_US

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